The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

The control's user interface varies from browser to browser; cross-browser support is currently a bit limited, with only Chrome/Opera and Microsoft Edge supporting it at this time. In non-supporting browsers, the control degrades gracefully to function identically to <input type="text">.

In Chrome/Opera the week control provides slots to fill in week and year values, a pop-up calendar interface to select them more visually, and an "X" button to clear the control's value.

The Edge week control is somewhat more elaborate, opening up week and year pickers with sliding reels.

You can set a default value for the input by including a value inside the value attribute, like so:

<label for="week">What week would you like to start?</label>
<input id="week" type="week" name="week" value="2017-W01">

One thing to note is that the displayed format may differ from the actual value, which is always formatted yyyy-Www. When the above value is submitted to the server, for example, browsers may display it as Week 01, 2017, but the submitted value will always look like week=2017-W01.

You can also get and set the value in JavaScript using the input element's value property, for example:

The stepping interval (the distance between allowed values) to use for both user interface and constraint validation

max

The latest (time-wise) year and week number, in the string format discussed in the Value section above, to accept. If the value entered into the element exceeds this, the element fails constraint validation. If the value of the max attribute isn't a valid week string, then the element has no maximum value.

This value must be greater than or equal to the year and week specified by the min attribute.

min

The earliest year and week to accept. If the value of the element is less than this, the element fails constraint validation. If a value is specified for min that isn't a valid week string, the input has no minimum value.

This value must be less than or equal to the value of the max attribute.

readonly

A Boolean attribute which, if present, means this field cannot be edited by the user. Its value can, however, still be changed by JavaScript code directly setting the HTMLInputElement.value property.

Note: Because a read-only field cannot have a value, required does not have any effect on inputs with the readonly attribute also specified.

step

The step attribute is a number that specifies the granularity that the value must adhere to, or the special value any, which is described below. Only values which are equal to the basis for stepping (min if specified, value otherwise, and an appropriate default value if neither of those is provided) are valid.

A string value of any means that no stepping is implied, and any value is allowed (barring other constraints, such as min and max).

Note: When the data entered by the user doesn't adhere to the stepping configuration, the user agent may round to the nearest valid value, preferring numbers in the positive direction when there are two equally close options.

For week inputs, the value of step is given in weeks, with a scaling factor of 604,800,000 (since the underlying numeric value is in milliseconds). The default value of step is 1, indicating 1week. The default stepping base is -259,200,000, which is the beginning of the first week of 1970 ("1970-W01").

At this time, it's unclear what a value of "any" means for step when used with week inputs. This will be updated as soon as that information is determined.

Using week inputs

Week inputs sound convenient at first glance, since they provide an easy UI for choosing weeks, and they normalize the data format sent to the server, regardless of the user's browser or locale. However, there are issues with <input type="week"> because browser support is not guaranteed across all browsers.

We'll look at basic and more complex uses of <input type="week">, then offer advice on mitigating the browser support issue later on (see Handling browser support).

Basic uses of week

The simplest use of <input type="week"> involves a basic <input> and <label> element combination, as seen below:

Controlling input size

<input type="week"> doesn't support form sizing attributes such as size. You'll have to resort to CSS for sizing needs.

Using the step attribute

You should be able to use the step attribute to vary the number of weeks jumped whenever they are incremented or decremented, however it doesn't seem to have any effect on supporting browsers.

Validation

By default, <input type="week"> does not apply any validation to entered values. The UI implementations generally don't let you specify anything that isn't a valid week/year, which is helpful, but it's still possible to submit with the field empty, and you might want to restrict the range of choosable weeks.

Setting maximum and minimum weeks

You can use the min and max attributes to restrict the valid weeks that can be chosen by the user. In the following example we are setting a minimum value of Week 01, 2017 and a maximum value of Week 52, 2017:

Here's the CSS used in the above example. Here we make use of the :valid and :invalid CSS properties to style the input based on whether or not the current value is valid. We had to put the icons on a <span> next to the input, not on the input itself, because in Chrome the generated content is placed inside the form control, and can't be styled or shown effectively.

If you try to submit the form with no value, the browser displays an error. Try playing with the example now:

Here's'a screenshot for those of you who aren't using a supporting browser:

Important: HTML form validation is not a substitute for scripts that ensure that the entered data is in the proper format. It's far too easy for someone to make adjustments to the HTML that allow them to bypass the validation, or to remove it entirely. It's also possible for someone to simply bypass your HTML entirely and submit the data directly to your server. If your server-side code fails to validate the data it receives, disaster could strike when improperly-formatted data is submitted (or data which is too large, of the wrong type, and so forth).

Handling browser support

As mentioned above, the major problem with using week inputs right now is browser support: Safari and Firefox don't support it on desktop, and old versions of IE don't support it.

Mobile platforms such as Android and iOS make really good use of such input types, providing specialist UI controls that make it really easy to select values in a touchscreen environment. For example, the week picker on Chrome for Android looks like this:

Non-supporting browsers gracefully degrade to a text input, but this creates problems both in terms of consistency of user interface (the presented control will be different), and data handling.

The second problem is the more serious. As mentioned earlier, with a week input the actual value is always normalized to the format yyyy-Www. When the browser falls back to a generic text input, there's nothing to guide the user toward correctly formatting the input (and it's certainly not intuitive). There are multiple ways in which people could write week values; for example:

Week 1 2017

Jan 2-8 2017

2017-W01

etc.

The best way to deal with week/years in forms in a cross-browser way at the moment is to get the user to enter the week number and year in separate controls (<select> elements being popular; see below for an example), or use JavaScript libraries such as jQuery date picker.

Examples

In this example we create two sets of UI elements for choosing weeks: a native picker created using <input type="week">, and a set of two <select> elements for choosing weeks/years in older browsers that don't support the week input type.

The other part of the code that may be of interest is the feature detection code. To detect whether the browser supports <input type="week">, we create a new <input> element, try setting its type to week, then immediately check what its type is set to. Non-supporting browsers will return text, because the week type falls back to type text. If <input type="week"> is not supported, we hide the native picker and show the fallback picker UI (<select>s) instead.